11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10.317
The Feeding Ecology Of Select Herbivorous Fishes in Two Reef Habitats Of Cuba
Alain DURÁN 1 , Rodolfo CLARO* 1
1 Departamento de Biología Marina, Instituto de Oceanología, La Habana, Cuba
The feeding activity and the impact of three herbivorous fishes (Sparisoma viride, Scarus
iserti and Acanthurus coeruleus) was studied at two coral reefs during the dry (February)
and rainy (August) seasons of 2006. The reef at Acuario (National Park Guanahacabibes)
is relatively pristine, while the reef at the north coast of Havana City (IdO) is subjected to
pollution and fishing pressure. Herbivore fish composition and foraging intensity were
measured for all Acanthurid and Scarid species, by measuring the total bite rates per 1 m2
of reef substrate during 5 minutes intervals (25 replicates). Concurrently, species
foraging intensity was mesured for juvenile, intermediate, and adult phases number of
bites in 10 min., 10 replicates). Algal consumption rate was estimated using a coefficent
of consumed biomass per bite, for each size class. The algal cover was sampled at 20 m
linear transects with 4 replicates at each site. Food items were assessed sampling algae at
the observed bited substrates. Compared to Acuario, herbivores in IdO showed lower
species richness and higher density, with the exception of large-sized parrotfish, which
were almost absent due to intense fishing. The highest bite rate was observed for the
smallest fish size, but net comsuption rate was three times greater in adult fishes. S.
viride had lower levels of foraging intensity than A. coeruleus and S. iserti, possibly due
to larger consumption per bite. Levels of foraging activity were lower in February. Algal
cover was lower in Acuario where herbivore density was higher but fish size was smaller.
In both locations epilithic algae were the preferred food.
10.318
Variation in Social Foraging By Fishes Across A Coral Reef Landscape
Peter AUSTER* 1 , James LINDHOLM 2
1 University of Connecticut, Groton, CT, 2 California State University Monterey Bay,
Seaside, CA
Coral reef landscapes are composed of a matrix of habitats which exhibit a gradient of
complexity at multiple spatial scales. This variation has been shown, in part, to influence
the composition of fish communities. It follows that such variation will also influence
the type and rate of species interactions. In this study, we quantified the rates of social
foraging bouts in relation to community composition across four distinct habitat types
(continuous reef, coral rubble-sand, reef edge, and spur and groove) at Conch Reef in the
Florida Keys National Marine Sanctuary (USA). The purpose of dividing the reef
landscape into particular habitat units was to ascertain if rates of social foraging vary in
consistent ways in relation to habitat attributes. Results indicated that there while there
were no clear divisions in species composition that could be correlated with habitat type,
comparisons of rates of social foraging based on total (mixed and single species foraging
groups) and mixed species bouts alone showed that rates of social foraging across
habitats were not equal. Further, both Fishers diversity and species richness measures
were not equal across habitat types, with lowest mean values in coral rubble habitat
where rates of social foraging were highest. These results highlight the complexity of
facilitative species interactions in coral reef landscapes.
10.319
Recruitment Potential And Recruitment Survival As A Function Of Habitat Degradation
Suzanne MILLS* 1 , David LECCHINI 2 , Pascal DUMAS 2 , Eric PARMENTIER 3
1 Biologie et Ecologie Tropicale et Méditerranéenne, UMR 5244 EPHE-CNRS-UPVD,
Perpignan, France, 2 UR 128 CoRéUs, Institute for Research and Development (IRD), Noumea,
New Caledonia, 3 Laboratoire de Morphologie Fonctionnelle et Evolutive, Université de Liège,
Liege, Belgium
Knowledge of the recruitment potential, as well as post-recruitment survival, between different
reef habitats, would improve the management of target species and conservation of reef
ecosystems. Many coral reefs have been subjected to, and continue to suffer from, habitat
degradation due to both natural and anthropogenic stress. However, the effects of habitat
degradation on larval recruitment potential and on the survival of settled recruits are currently
not known. We aimed to distinguish between these two processes by simultaneously measuring
survival and recruitment of vertebrate and invertebrate larvae across habitats differing in their
percentage of coral cover (healthy vs dead: 50 % vs 12 % coral cover) with a 100 % sand
habitat as a control. Recruitment and survival were monitored after 10, 20, 40 and 80 days on
atolls in French Polynesia. Lower recruitment was identified for multiple molluscan, gastropod
and sponge species in the control sand habitat, possibly reflecting the lack of habitat and/or
conspecifics attraction cues, either acoustic or chemical. On the other hand polychaetes and
opistobranchs showed higher recruitment in control sand habitats. One molluscan species, the
pearl oyster, of considerable economic importance in French Polynesia, showed lower growth
in the control sand habitat. Differences in recruitment and survival will be discussed as a
function of coral cover and habitat degradation, as well as consequences for reef ecosystem
conservation and management.
10.320
Effect of the Herbivorous West Indian Spider Crab (Mithrax spinosissimus) on Patch
Reef Algal Communities in the Florida Keys (USA)
Angela MOJICA* 1 , Mark BUTLER 1
1 Biological Sciences, Old Dominion University, Norfolk, VA
Many Caribbean coral reefs have changed from coral- to algal- dominance, and the decline of
piscine and echinoderm grazers in these communities has played a significant role in this phaseshift.
Virtually unknown, however, is the effect of the herbivorous West Indian spider crab
(Mithrax spinosissimus) on coral reef community structure. Therefore we examined the
foraging ecology and impact of spider crab herbivory on inshore patch reefs in the Florida
Keys, Florida (USA). Crabs were held individually for 24 hrs and fed either four naturallyoccurring
algae (Ulva sp., Laurencia sp., Dyctiota sp., and Halimeda sp.), or clumps of mixed
macro-algae (Halimeda sp. + Dyctiota sp.) from the reef to determine diet preferences and
consumption of crabs by size and sex. Preliminary analysis of these results showed that fleshy
macro algae are preferred by M. spinossissimus over Halimeda sp. Rates of consumption
obtained under laboratory conditions were compared with those obtained in the field, by
encaging a single crab in cages that excluded all herbivores greater than 2cm in diameter. Rates
of benthic algal production and macroalgal growth, estimated in situ on caged and un-caged
natural plots and experimental plates surpassed the consumption rates possible by individual
crabs. Our results indicate that M. spinosissimus as potential important consumers of
macroalgae on reefs, but their ability to regulate reef macro-algal abundance or composition is
diminished by their low density, low mobility, and perhaps lower activity in predator-rich
environments such as reefs.
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